The present invention relates to a method and apparatus for evaluating color image signals available from, for example, CCD color image sensors fabricated as semiconductor IC's.
Heretofore there have been put to practical use a wide variety of semiconductor CCD color image sensors which have mosaic color filters or stripe color filters coated on their front for creating color image signals.
The semiconductor CCD image sensors are produced using the IC technology but they may sometimes be defective from various causes in their manufacturing process. In the case of the color image sensor, in particular, color reproduction errors such as shading shown in FIG. 1 and stripes of colors shown in FIG. 2 are induced owing to defects of the image sensor itself. The shading in FIG. 1 is a color reproduction error that the reproduced picture, which ought to be white, is colored over a wide area (at the upper left in FIG. 1). The bands of colors in FIG. 2 are slanted or vertical colored stripes which appear in the reproduced picture which ought to be white.
Conventionally, such color reproduction errors are detected through visual inspection of a display image provided on a CRT display screen by the color image signal output from the color image sensor shed evenly all over its light receiving surface by standard white light. The conventional testing of color image sensors thus involves direct visual inspection of the color reproduction errors by test personnel, and hence is inefficient. Further, the traditional inspection of color image sensors calls for many test personnel at the mass-production site, in particular; consequently, this goes against labor saving and does not lead to the reduction of manufacturing costs of color image sensors. Besides, clear-cut color patterns can be detected without any individual difference among test personnel but pale color patterns may sometimes escape particular test personnel's notice.